reproduce (this is a W=1 build):
        # https://github.com/jimc/linux/commit/69e3e77dca408ade14290862bf4cc991166d5acd
        git remote add jimc https://github.com/jimc/linux.git
        git fetch --no-tags jimc dd-shrink-4b
        git checkout 69e3e77dca408ade14290862bf4cc991166d5acd
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash CLIPPY=1 rustdoc